In clinical examination for medical diagnosis, protein, sugar, lipid, enzyme, hormone, inorganic ions, disease markers, and the like in biological samples, such as blood and urine, are biochemically analyzed and immunologically analyzed. In clinical examination, it is necessary to treat a plurality of examination items with high reliability at high speed, and therefore, most of them are performed by an automatic analyzer. As the automatic analyzer, for example, a biochemistry analyzer that performs biochemical analysis by using, as an object to be analyzed, a reaction solution obtained by mixing a sample, such as serum, with the desired reagent for reaction, and measuring the absorbance of the reaction solution is known. A biochemistry analyzer of this type includes containers containing samples and reagents, and reaction Cells into which the samples and the reagents are to be injected, and includes dispensing mechanisms including dispensing nozzles for automatically injecting the sample and the reagent into the reaction Cell, an automatic stirring mechanism having a stirring bar for mixing the sample and the reagent in the reaction Cell, a mechanism for measuring the absorbance of the sample during reaction or after the completion of the reaction, an automatic washing mechanism for sucking and discharging the reaction solution after the completion of the measurement and washing the reaction Cell, and the like (for example, Patent Literature 1).
In such an automatic analyzer, generally, a large number of samples and reagents are dispensed in turn by the dispensing nozzles. For example, the sample dispensing nozzle takes a predetermined amount of a sample from a container containing the sample, such as a blood collection tube, and discharges the sample into a reaction Cell for the reaction of a reagent. The reagent dispensing nozzle discharges into the reaction Cell a predetermined amount of a reagent taken from a container containing the reagent. At this time, if the components of the dispensed liquid remaining on the dispensing nozzle surface are mixed into the next dispensed liquid, the measurement result may be affected. This is referred to as carry over.
The problem of carry over is deeply related to a demand for trace amounts of samples and reagents in the field of automatic analyzers in recent years. With the increase of the number of analysis items, the amount of a sample that can be used for one analysis item becomes smaller. The sample itself is precious and cannot be prepared in a large amount in some cases, and there is also a demand for higher sensitivity. In addition, as the analysis content becomes more sophisticated, generally, the reagent becomes more expensive, and there is a requirement for trace amounts of reagents also in terms of cost. Due to the increase of such a demand for trace amounts of samples and reagents, the diameter of the dispensing nozzle becomes smaller, and the outer diameter of the tube is about 0.5 mm. A very small nozzle diameter increases the proportion of the surface area to the volume of a dispensed solution. Therefore, the importance of controlling the adsorption of substances on the dispensing nozzle surface to reduce carry over increases.
In addition, when a sample for the analysis of biochemistry items, and immunity items with a wide measurement concentration range is taken from the same container and measured, it is required to reduce carry over between samples by a dispensing nozzle as much as possible.
In order to reduce carry over, conventionally, washing with pure water or a detergent containing a surfactant has been carried out (Patent Literature 2). A method of deactivating adhering sample residues with active oxygen is also known (Patent Literature 3). A method using a disposable nozzle (disposable tip), which can be thrown away after one use, is also known as one of methods for solving carry over.
XPS (X-ray photo electron spectroscopy) and the like are widely used for the quantification and composition analysis of chemical substances adsorbed on a surface, and, for example, analysis is performed for the composition of monomolecular films, such as self-assembled monolayers, and the quantification of chemical species (Non Patent Literatures 1 and 2). Like these, quantification can be performed by XPS also for the quantification of protein remaining on a surface (Non Patent Literature 3).